This application is based on application No. 275045/1999 filed in Japan, the contents of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly, to an image forming apparatus so adapted as to supply toners to an image carrying member from a developing device, form a toner image on a surface of the image carrying member, transfer the toner image to a recording medium from the image carrying member, press a pressing member against the surface of the image carrying member after the transfer, and remove the toners remaining on the surface of the image carrying member, characterized in that the pressing member is prevented from immediately wearing and causing irregularities in the surface of the image carrying member, to stably remove the toners remaining on the surface of the image carrying member.
2. Description of the Related Art
In a conventional example of image forming apparatuses such as electrophotographic copying machines or printers, an image carrying member 10 in which a photoreceptor 12 is formed on a surface of a conductive base member 11 in a drum shape is rotated, a surface of the image carrying member 10 is charged by a charging device 20, and the surface of the image carrying member 10 is then subjected to exposure corresponding to image information by a latent image forming device 30 using a laser or the like, to form an electrostatic latent image on the surface of the image carrying member 10, as shown in FIG. 1. Toners 41 are supplied to the surface, on which the electrostatic latent image has been thus formed, of the image carrying member 10 from a developing device 40, to form a toner image corresponding to the electrostatic latent image on the surface of the image carrying member 10.
Thereafter, a recording medium 51 such as a recording paper sheet is introduced into a portion between the image carrying member 10 and a transferring device 50 such as a transfer roller by a feed roller 52, to transfer the toner image formed on the surface of the image carrying member 10 to the recording medium 51 by the transferring device 50.
The toner image which has been thus transferred to the recording medium 51 is then fixed to the recording medium 51 by a fixing device 60 such as a fixing roller. On the other hand, a pressing member 70 in a plate shape is pressed against the surface of the image carrying member 10 after the transfer, to remove the toners 41 or the like remaining on the surface of the image carrying member 10 from the surface of the image carrying member 10. Thereafter, the surface of the image carrying member 10 is charged by the charging device 20, as described above. The above-mentioned operations are repeated, to successively form toner images.
When the pressing member 70 is pressed against the surface of the image carrying member 10, to remove the toners 41 or the like remaining on the surface of the image carrying member 10 from the surface of the image carrying member 10, as described above, the pressing member 70 which is pressed against the image carrying member 10 gradually wears, so that the toners 41 or the like remaining on the surface of the image carrying member 10 cannot be sufficiently removed. Further, the pressing member 70 causes irregularities in the surface of the image carrying member 10. The irregularities prevent the toners 41 or the like from being suitably removed by the pressing member 70. Consequently, noise based on insufficient cleaning appears in the formed toner image.
In recent years, in supplying a lubricant to the surface of the image carrying member 10 and passing the lubricant through the pressing member 70, the lubricant has been rolled by the pressing member 70, to form a film of the lubricant on the surface of the image carrying member 10. The film of the lubricant has prevented the pressing member 70 from wearing and causing irregularities in the surface of the image carrying member 10.
In the conventional example, in supplying the lubricant to the surface of the image carrying member 10, the lubricant is added to the toners 41 in the developing device 40, and the lubricant, together with the toners 41, is supplied to the surface of the image carrying member 10, as in the image forming apparatus shown in FIG. 1. Alternatively, the lubricant is scraped off a molding 81 of the lubricant by a brush 82, and the lubricant is supplied to the surface of the image carrying member 10 from the brush 82, as shown in FIG. 2.
When the lubricant is added to the toners 41, as described above, however, the performance of the toners 41 changes depending on the type of the lubricant. Consequently, a good toner image cannot be obtained.
When the lubricant, together with the toners 41, is supplied to the surface of the image carrying member 10, in a state where the toners 41 or the like remaining on the surface of the image carrying member 10 after the transfer are removed from the surface of the image carrying member 10 by the pressing member 70, the toners 41, a post-treatment agent added to the toners 41, and so forth are stored in a contact portion between the pressing member 70 and the image carrying member 10. In the portion where the toners 41, the post-treatment agent, and so forth are stored, the lubricant is not introduced into the pressing member 70. Accordingly, the film of the lubricant is not satisfactorily formed on the surface of the image carrying member 10. Consequently, the pressing member 70 still wears and causes irregularities in the surface of the image carrying member 10.
In scraping the lubricant off the molding 81 of the lubricant by the brush 82 and supplying the lubricant to the surface of the image carrying member 10, as described above, the lubricant is always supplied to the surface of the image carrying member 10 by the brush 82 in the conventional example.
In a state where the toner image is formed, however, the toners 41, the post-treatment agent, and so forth are stored in the contact portion between the pressing member 70 and the image carrying member 10, as described above. Accordingly, the film of the lubricant is not satisfactorily formed on the surface of the image carrying member, as in the above-mentioned case. Consequently, the lubricant is uselessly consumed.
When the lubricant is scraped off the molding 81 of the lubricant by the brush 82 and is supplied to the surface of the image carrying member 10, as described above, the particle diameter of the lubricant supplied to the surface of the image carrying member 10 by the brush 82 is not fixed. Accordingly, the lubricant having a large particle diameter, together with the toners 41, is removed from the surface of the image carrying member 10 by the pressing member 70. On the other hand, the lubricant 70 having a small particle diameter is not satisfactorily rolled by the pressing member 70. Consequently, the film of the lubricant is not suitably formed on the surface of the image carrying member 10.
Furthermore, in scraping the lubricant off the molding 81 of the lubricant by the brush 82 and supplying the lubricant to the surface of the image carrying member 10, as described above, if the diameter of the image carrying member 10 to be used is small, the places where the brush 82 and the molding 81 of the lubricant are provided are a problem.